In a world where "ramming" and "griefing" are options that are there, "wrong way" is too general? So, what, should ramming be changed because it doesn't have options for "head on ramming", "sideswiping" and "rear-ending"?
People driving the wrong way in the UK will usually realise their mistake in time if you honk at them, but can crash before they do and (shock-horror) go the wrong way on purpose.
You'd swear reporting someone makes their computer explode. It alone doesn't hurt anyone. It just gets the attention of an admin, who will then determine if it's a genuine mistake or not and take a course of action.
The "proper" report system is clogged up by about a week. Reporting in-game allows for instant action to be taken, potentially preventing further accidents.
Reporting people overtaking accidents will do nothing (and if people want to do this, they already can with the system as it is right now, so silly point to make), if it was a once-off overtake an admin that comes and views the player will see them do nothing wrong and do nothing.
ON THE FLIPSIDE: Say a serial overtaker is reported for wrong way driving. The admin comes and sees them on the correct side of the road but follows them around for a few seconds. They see them starting to overtake a line of traffic and can ban them on the spot. Same with someone driving 150+ km/h in the UK on the wrong side for extended periods of time.
That "annoyance" is simply a holdover from a time when the only way to report someone was typing "/report" in chat. The muscle memory stayed, and some newer players must have thought typing report constituted a report. Not quite "age old" as you put it, common practice until the tab menu reporting was added.